Caernarfon Castle is called the most imposing of Edward I's castles, and I definitely agree.
It is gigantic! I spent a few hours trying to see everything, I still didn't get everywhere. There were so many passageways and corridors to explore, different levels of walkways - it would have been easy to get lost!
And this castle was actually never finished - he ran out of money before it was completed, and while work continued over the years, there were still missing walls and the kitchen was never finished. However there was a system of pipes to bring water directly to the kitchen!
Here is Edward I who built or rebuilt all of the castles I have visited so far.
I also visited Segontium, a Roman fort here, but all that were left were foundations which don't make a good picture!
The hostel I'm staying in is right inside the city walls - Caernarfon is another walled town, but on a smaller scale than Conwy. In the 1800s the town wanted to tear down the castle and the walls, but luckily they were overruled. Lots of buildings though were built right into the existing wall, like this church: